Conducting paths and nerve centers of the auditory analyzer. auditory pathway auditory pathway

The conductive path of the auditory analyzer connects the organ of Corti with the overlying parts of the central nervous system. The first neuron is located in the spiral node, located at the base of the hollow cochlear node, passes through the channels of the bone spiral plate to the spiral organ and ends at the outer hair cells. The axons of the spiral ganglion make up the auditory nerve, which enters the brainstem in the region of the cerebellopontine angle, where they end in synapses with the cells of the dorsal and ventral nuclei.

The axons of the second neurons from the cells of the dorsal nucleus form the brain strips located in the rhomboid fossa on the border of the bridge and the medulla oblongata. Most of the brain strip passes to the opposite side and, near the midline, passes into the substance of the brain, connecting to the lateral loop of its side. The axons of the second neurons from the cells of the ventral nucleus are involved in the formation of the trapezoid body. Most of the axons pass to the opposite side, switching in the superior olive and nuclei of the trapezoid body. A smaller part of the fibers ends on its side.

The axons of the nuclei of the superior olive and trapezoid body (III neuron) are involved in the formation of the lateral loop, which has fibers of II and III neurons. Part of the fibers of the II neuron are interrupted in the nucleus of the lateral loop or switched to the III neuron in the medial geniculate body. These fibers of the III neuron of the lateral loop, passing by the medial geniculate body, end in the lower colliculus of the midbrain, where tr.tectospinalis is formed. Those fibers of the lateral loop related to the neurons of the superior olive, from the bridge penetrate into the upper legs of the cerebellum and then reach its nuclei, and the other part of the axons of the superior olive goes to the motor neurons of the spinal cord. The axons of the III neuron, located in the medial geniculate body, form the auditory radiance, ending in the transverse Heschl gyrus of the temporal lobe.

The central representation of the auditory analyzer.

In humans, the cortical auditory center is the transverse gyrus of Heschl, including, in accordance with Brodmann's cytoarchitectonic division, fields 22, 41, 42, 44, 52 of the cerebral cortex.

In conclusion, it should be said that, as in other cortical representations of other analyzers in the auditory system, there is a relationship between the zones of the auditory cortex. Thus, each of the zones of the auditory cortex is connected with other zones organized tonotopically. In addition, there is a homotopic organization of connections between similar zones of the auditory cortex of the two hemispheres (there are both intracortical and interhemispheric connections). At the same time, the main part of the bonds (94%) homotopically terminate on the cells of layers III and IV, and only a small part - in layers V and VI.

94. Vestibular peripheral analyzer. On the eve of the labyrinth there are two membranous sacs with the otolith apparatus in them. On the inner surface of the sacs there are elevations (spots) lined with neuroepithelium, consisting of supporting and hair cells. The hairs of sensitive cells form a network, which is covered with a jelly-like substance containing microscopic crystals - otoliths. With rectilinear movements of the body, otoliths are displaced and mechanical pressure occurs, which causes irritation of neuroepithelial cells. The impulse is transmitted to the vestibular node, and then along the vestibular nerve (VIII pair) to the medulla oblongata.

On the inner surface of the ampullae of the membranous ducts there is a protrusion - an ampullar comb, consisting of sensitive neuroepithelial cells and supporting cells. Sensitive hairs sticking together are presented in the form of a brush (cupula). Irritation of the neuroepithelium occurs as a result of the movement of the endolymph when the body is displaced at an angle (angular accelerations). The impulse is transmitted by the fibers of the vestibular branch of the vestibulocochlear nerve, which ends in the nuclei of the medulla oblongata. This vestibular zone is connected with the cerebellum, spinal cord, nuclei of the oculomotor centers, and the cerebral cortex.

In accordance with the associative links of the vestibular analyzer, vestibular reactions are distinguished: vestibulosensory, vestibulo-vegetative, vestibulosomatic (animal), vestibulocerebellar, vestibulospinal, vestibulo-oculomotor.

95. Conductive path of the vestibular (statokinetic) analyzer provides the conduction of nerve impulses from the hair sensory cells of the ampullar scallops (ampulla of the semicircular ducts) and spots (elliptical and spherical sacs) to the cortical centers of the cerebral hemispheres.

The bodies of the first neurons of the statokinetic analyzer lie in the vestibular node, located at the bottom of the internal auditory canal. The peripheral processes of the pseudounipolar cells of the vestibular ganglion terminate on the hairy sensory cells of the ampullar ridges and spots.

The central processes of pseudounipolar cells in the form of the vestibular part of the vestibulocochlear nerve, together with the cochlear part, enter the cranial cavity through the internal auditory opening, and then into the brain to the vestibular nuclei lying in the vestibular field, area vesribularis of the rhomboid fossa

The ascending part of the fibers ends on the cells of the superior vestibular nucleus (Bekhterev *) The fibers that make up the descending part end in the medial (Schwalbe **), lateral (Deiters ***) and lower Roller ****) vestibular nuclei pax

Axons of cells of the vestibular nuclei (II neurons) form a series of bundles that go to the cerebellum, to the nuclei of the nerves of the eye muscles, the nuclei of the autonomic centers, the cerebral cortex, to the spinal cord

Part of cell axons lateral and superior vestibular nucleus in the form of a vestibulo-spinal tract, it is directed to the spinal cord, located along the periphery at the border of the anterior and lateral cords and ends segmentally on the motor animal cells of the anterior horns, carrying out vestibular impulses to the muscles of the neck of the trunk and extremities, ensuring the maintenance of body balance

Part of axons of neurons lateral vestibular nucleuspa is directed to the medial longitudinal bundle of its and the opposite side, providing a connection of the balance organ through the lateral nucleus with the nuclei of the cranial nerves (III, IV, VI nar), innervating the muscles of the eyeball, which allows you to maintain the direction of gaze, despite changes in the position of the head. Maintaining the balance of the body is largely dependent on the coordinated movements of the eyeballs and head.

Axons of cells of the vestibular nuclei form connections with neurons of the reticular formation of the brain stem and with the nuclei of the tegmentum of the midbrain

The appearance of vegetative reactions(slowing of the pulse, drop in blood pressure, nausea, vomiting, blanching of the face, increased peristalsis of the gastrointestinal tract, etc.) in response to excessive irritation of the vestibular apparatus can be explained by the presence of connections between the vestibular nuclei through the reticular formation with the nuclei of the vagus and glossopharyngeal nerves

Conscious determination of the position of the head is achieved by the presence of connections vestibular nuclei with the cerebral cortex At the same time, the axons of the cells of the vestibular nuclei pass to the opposite side and are sent as part of the medial loop to the lateral nucleus of the thalamus, where they switch to III neurons

Axons of III neurons pass through the back of the posterior leg of the internal capsule and reach cortical nucleus stato-kinetic analyzer, which is scattered in the cortex of the superior temporal and postcentral gyri, as well as in the superior parietal lobe of the cerebral hemispheres

96. Foreign bodies in the external auditory canal most often found in children when, during the game, they push various small objects into their ears (buttons, balls, pebbles, peas, beans, paper, etc.). However, in adults, foreign bodies are often found in the external auditory canal. They can be fragments of matches, pieces of cotton wool that get stuck in the ear canal at the time of cleaning the ear from sulfur, water, insects, etc.

Clinical picture depends on the size and nature of foreign bodies of the outer ear. So, foreign bodies with a smooth surface usually do not injure the skin of the external auditory canal and may not cause discomfort for a long time. All other items quite often lead to reactive inflammation of the skin of the external auditory canal with the formation of a wound or ulcerative surface. Foreign bodies swollen from moisture, covered with earwax (cotton wool, peas, beans, etc.) can lead to blockage of the ear canal. It should be borne in mind that one of the symptoms of a foreign body in the ear is hearing loss as a violation of sound conduction. It occurs as a result of a complete blockage of the ear canal. A number of foreign bodies (peas, seeds) are capable of swelling under conditions of humidity and heat, so they are removed after the infusion of substances that contribute to their wrinkling. Insects caught in the ear, at the time of movement, cause unpleasant, sometimes painful sensations.

Diagnostics. Recognition of foreign bodies is usually not difficult. Large foreign bodies linger in the cartilaginous part of the ear canal, and small ones can penetrate deep into the bone section. They are clearly visible with otoscopy. Thus, the diagnosis of a foreign body of the external auditory canal should and can be made with otoscopy. In cases where, with unsuccessful or inept attempts to remove a foreign body made earlier, inflammation has occurred with infiltration of the walls of the external auditory canal, diagnosis becomes difficult. In such cases, if a foreign body is suspected, short-term anesthesia is indicated, during which both otoscopy and removal of the foreign body are possible. X-rays are used to detect metallic foreign bodies.

Treatment. After determining the size, shape and nature of the foreign body, the presence or absence of any complication, a method for its removal is chosen. The safest method of removing uncomplicated foreign bodies is to wash them out with warm water from a Janet-type syringe with a capacity of 100-150 ml, which is carried out in the same way as removing the sulfuric plug.
When you try to remove it with tweezers or forceps, a foreign body can slip out and penetrate from the cartilaginous section into the bony section of the ear canal, and sometimes even through the tympanic membrane into the middle ear. In these cases, the extraction of a foreign body becomes more difficult and requires great care and good fixation of the patient's head, short-term anesthesia is necessary. The hook of the probe must be passed behind the foreign body under visual control and pulled out. A complication of instrumental removal of a foreign body can be a rupture of the eardrum, dislocation of the auditory ossicles, etc. Swollen foreign bodies (peas, beans, beans, etc.) must first be dehydrated by infusing 70% alcohol into the ear canal for 2-3 days, as a result of which they shrink and are removed without much difficulty by washing.
Insects in contact with the ear are killed by infusing a few drops of pure alcohol or heated liquid oil into the ear canal, and then removed by rinsing.
In cases where a foreign body has wedged into the bone section and caused a sharp inflammation of the tissues of the ear canal or led to an injury to the eardrum, they resort to surgical intervention under anesthesia. An incision is made in the soft tissues behind the auricle, the posterior wall of the skin auditory canal is exposed and cut, and the foreign body is removed. Sometimes it is necessary to surgically expand the lumen of the bone section by removing part of its posterior wall.

The first neuron of the auditory analyzer pathways is the bipolar cells mentioned above. Their axons form the cochlear nerve, the fibers of which enter the medulla oblongata and terminate in the nuclei, where the cells of the second neuron of the pathways are located. The axons of the cells of the second neuron reach the internal geniculate body,

Rice. 5. Scheme of the conduction paths of the auditory analyzer:

1 - receptors of the organ of Corti; 2 - bodies of bipolar neurons; 3 - cochlear nerve; 4 - nuclei of the medulla oblongata, where the bodies of the second neuron of the pathways are located; 5 - internal geniculate body, where the third neuron of the main pathways begins; 6 - the upper surface of the temporal lobe of the cerebral cortex (lower wall of the transverse fissure), where the third neuron ends; 7 - nerve fibers connecting both internal geniculate bodies; 8 - posterior tubercles of the quadrigemina; 9 - the beginning of the efferent paths coming from the quadrigemina.

mostly on the opposite side. Here begins the third neuron, through which the impulses reach the auditory region of the cerebral cortex (Fig. 5).

In addition to the main pathway connecting the peripheral part of the auditory analyzer with its central, cortical part, there are other ways through which reflex reactions to irritation of the hearing organ in the animal can occur even after the removal of the cerebral hemispheres. Of particular importance are orienting reactions to sound. They are carried out with the participation of the quadrigemina, to the posterior and partly anterior tubercles of which there are collaterals of fibers heading to the internal geniculate body.

Cortical division of the auditory analyzer.

In humans, the core of the cortical section of the auditory analyzer is located in the temporal region of the cerebral cortex. In that part of the surface of the temporal "region, which is the lower wall of the transverse, or Sylvian, fissure, field 41 is located. To it, and possibly to the adjacent shelf" 42, the main mass of fibers is directed from the internal geniculate body. Observations have shown that with bilateral destruction of these fields, complete deafness sets in. However, in cases where the lesion is limited to one hemisphere, a slight and often only temporary hearing loss may occur. This is due to the fact that the pathways of the auditory analyzer do not completely cross. In addition, both internal geniculate bodies are connected between they are intermediate neurons through which impulses can pass from the right side to the left and vice versa.As a result, the cortical cells of each hemisphere receive impulses from both Corti's organs.

From the cortical section of the auditory analyzer, efferent paths go to the underlying parts of the brain, and above all to the internal geniculate body and to the posterior tubercles of the quadrigemina. Through them, cortical motor reflexes to sound stimuli are carried out. By stimulating the auditory region of the cortex, one can evoke an orienting reaction of alertness in the animal (movements of the auricle, turning of the head, etc.). Analysis and synthesis of sound irritation. The analysis of sound stimuli begins in the peripheral part of the auditory analyzer, which is ensured by the structural features of the cochlea, and above all the main plate, each section of which fluctuates in response to sounds of only a certain height.

Higher analysis and synthesis of sound stimulation, based on the formation of positive and negative conditioned connections, occurs in the cortical section of the analyzer. Each sound perceived by the organ of Corti leads to a state of excitation of certain cellular groups of field 41 and the fields adjacent to it. From here, excitation spreads to other points of the cerebral cortex, especially to fields 22 and 37. Between the various cell groups that repeatedly came to the state of excitation under the influence of a particular sound stimulation or a complex of successive sound stimulations, more and more strong conditional connections are established. They are also established between the foci of excitation in the auditory analyzer and those foci that simultaneously arise under the influence of stimuli acting on other analyzers. Thus, more and more new conditional connections are formed, enriching the analysis and synthesis of sound stimulation.

The analysis and synthesis of sound speech stimuli is based on the establishment of conditional connections between the foci of excitation. which arise under the influence of direct stimuli acting on various analyzers, and those foci that are caused by sound speech signals that designate these stimuli. The so-called auditory center of speech, i.e. that part of the auditory analyzer, whose function is associated with speech analysis and the synthesis of sound stimuli, in other words, with the understanding of audible speech, is located mainly in the left hemisphere and occupies the posterior end of the field and the adjacent section of the field.

Factors that determine the sensitivity of the auditory analyzer.

The human ear is especially sensitive to the frequency of sound and - vibrations from 1030 to 40 EE per second. Sensitivity to higher and lower sounds drops significantly, especially as you approach the lower and upper limits of perceived frequencies. So, for sounds whose oscillation frequency approaches 20 or 20,000 per second, the threshold rises by a factor of 10 ROE, if we determine the strength of the sound by the pressure it produces. With age, the sensitivity of the auditory analyzer, as a rule, decreases significantly, but mainly to high-frequency sounds, while to low ones (up to 1000 oscillations per second) it remains almost unchanged until old age.

In conditions of complete silence, the sensitivity of hearing increases. If, however, a tone of a certain height and constant intensity begins to sound, then, as a result of adaptation to it, the sensation of loudness decreases first quickly, and then more and more slowly. At the same time, although to a lesser extent, the sensitivity to sounds that are more or less close in frequency to the sounding tone decreases. However, adaptation usually does not cover the entire range of perceived sounds. When the sound stops due to adaptation to silence, the previous level of sensitivity is restored after 10-15 seconds.

In part, adaptation depends on the peripheral part of the analyzer, namely, on changes in both the amplifying function of the sound-conducting apparatus and the excitability of the hair cells of the organ of Corti. The central section of the analyzer also takes part in the phenomena of adaptation, as evidenced by the fact that when sound is applied to only one ear, shifts in sensitivity are observed in both ears. The sensitivity of the auditory analyzer, and in particular the process of adaptation, is influenced by changes in cortical excitability, which arise as a result of both irradiation and mutual induction of excitation and inhibition upon stimulation of the receptors of other analyzers. The sensitivity also changes with the simultaneous action of two tones of different heights. In the latter case, a weak sound is drowned out by a stronger one, mainly because the focus of excitation that arises in the cortex under the influence of a strong sound lowers, as a result of negative induction, the excitability of other parts of the cortical section of the same analyzer.

SEI HPE "ORENBURG STATE MEDICAL ACADEMY"

DEPARTMENT OF HUMAN ANATOMY

ANATOMY

SENSORS

Textbook for independent work of students

Orenburg 2008

Anatomy of the sense organs - a textbook for independent work of students, edited by associate professor N.I. Kramar and professor L.M. Zheleznov, Orenburg 2008. - 26 p.

The expediency of creating this manual is determined primarily by the sufficient complexity of the topic. In addition, only a good knowledge of the anatomy of the sense organs allows us to begin to consider the clinically important sections of medicine - otorhinolaryngology and ophthalmology.

The manual is illustrated with original adapted diagrams of the auditory, vestibular and visual pathways, the description of which in the available educational literature is interpreted by various authors ambiguously and differs in significant and unnecessary details.

These instructions include control questions to the topics of practical classes, the answers to which the student should know after self-study of the material, a list of visual aids is presented with an indication of the formations that should be demonstrated and commented on. A list of tables and other visual aids is given, on which the student should be able to find and show specific anatomical formations.

Assistant, Ph.D. Lutsay N.D.

Reviewers: Head of the Department of ENT Diseases, Professor I.A. Shulga, Head of the Department of Eye Diseases, Professor A.I. Kirillichev

Topic: "STRUCTURE AND DEVELOPMENT OF THE ORGANS OF HEARING AND

BALANCE"

test questions

1. Departments of the organ of hearing and balance.

2. Outer ear (auricle, external auditory canal, eardrum).

3. Middle ear (tympanic cavity, auditory tube, auditory ossicles and muscles).

4. Inner ear (bony and membranous labyrinths).

5. Ways of conducting sound.

6. Auditory pathway (conscious and unconscious portions).

7. Vestibular pathway (conscious and unconscious portions).

8. Phylogeny of the organ of hearing and balance.

9. Ontogeny of the organ of hearing and balance, its main developmental anomalies.

A set of drugs

1. Skull as a whole

2. Temporal bone

3. Model of the organ of hearing and balance (collapsible)

3. The brain stem.

4. Sagittal section of the brain.

5. Basal nuclei of the cerebral cortex.

6. Table diagram of the auditory pathway

Show

1. On the skull and temporal bone:

External auditory meatus;

Internal auditory meatus;

The roof of the tympanic cavity;

Mastoid process and Thorn's triangle;

Sleepy channel;

Jugular hole.

2. On a collapsible model of the organ of hearing and balance and tables:

- structural elements of the outer ear:

a. auricle with its curl, antihelix, tragus,

antitragus, lobule;

b. external auditory canal with its cartilaginous and bony parts;

in. eardrum;

- structural elements of the middle ear:

a. walls of the tympanic cavity:

Lateral (webbed);

Upper (tire);

Anterior (sleepy);

Back (mastoid);

Medial (labyrinth) with its vestibule and cochlear windows;

Overtympanic pocket;

b. tympanic messages:

On the back wall with the cave of the mastoid process;

On the anterior wall is the tympanic opening of the auditory tube;

in. contents of the tympanic cavity:

Auditory ossicles (hammer, anvil and stirrup);

Joints of the auditory ossicles: joints (anvil-malleolar,

anvil-stapes) and syndesmosis (between the base of the stirrup on the edges

vestibulum, between the malleus and the tympanic membrane).

The muscle of the stirrup and the muscle that strains the eardrum;

d. auditory tube with its bony and cartilaginous parts, tympanic and pharyngeal

holes;

- structural elements of the inner ear:

a. structures of the bony labyrinth:

The vestibule with its elements:

vestibular scallop;

Elliptical and spherical pockets,

Communications with the semicircular canals;

Communication with snail channel;

Anterior window with stirrup base;

Cochlear window with secondary tympanic membrane;

Semicircular canals (anterior, posterior, lateral) with their simple,

ampullar and common legs;

The cochlea with its base, dome, rod, spiral plate and

spiral channel;

b. parts of the membranous labyrinth:

Semicircular ducts (anterior, posterior and lateral) and their ampullar

scallops;

A matochka and a pouch with their spots;

Utero-saccular duct;

The cochlear duct with its:

outer wall;

vestibular wall;

Tympanic wall and organ of Corti;

Connecting duct;

in. perilymphatic space of semicircular canals, vestibule and cochlea

(vestibule and tympanic ladders, helicotrema);

d. endolymphatic space

3. On preparations of the brain stem, basal ganglia and hemispheres:

Mosto-cerebellar angle;

Triangle loop of the isthmus of the rhomboid brain;

Inferior colliculi of the midbrain with their handle;

Medial geniculate bodies;

Posterior leg of the internal capsule.

Superior temporal gyrus.

Draw and label:

1. Scheme of the bone and membranous labyrinths

2. Scheme of the auditory pathway

3. Diagram of the vestibular pathway

1. Ear - auris (Latin), otos (Greek);

2. Pre-door membrane - membrane vestibularis (lat.), Reissner's membrane (author);

3. The outer and inner surfaces of the superior temporal gyrus - Geschl's gyrus (ed.).

4. Spiral organ - organum spirale (lat.), Corti's organ (ed.).

Control questions for the lecture material

1. The meaning and function of the organ of hearing and balance.

2. Stages of phylogenesis of the organ of hearing and balance.

3. Ontogeny of the organ of vision:

Sources and process of formation of the auricle, external auditory canal

and tympanic membrane of the outer ear;

Sources and process of formation of the auditory tube, tympanic cavity, auditory

bones and auditory muscles of the middle ear;

Sources and process of formation of the membranous and bone labyrinths

inner ear.

4. The main anomalies in the development of the organ of hearing and balance:

Congenital deafness is a consequence of a deep violation of the formation

the inner ear and its connections;

Congenital hearing loss is a consequence of incomplete resorption of the embryonic

connective tissue around the auditory ossicles;

The location of the auricles on the neck, changes in the shape of the auricles -

the result of incorrect transformation of the material of I and II gill arches.

auditory pathway

General characteristics - sensitive (the human hearing organ perceives sounds in the range of 15 Hz - 20,000 Hz.), Conscious, 3-neural, crossed.

I neuron bipolar spiral ganglion cells. Their dendrites end on the hairy sensory (neurosensory) cells of the organ of Corti. Axons form the cochlear part of the vestibulocochlear nerve; in the region of the cerebellar pontine angle, they enter the pons, where they switch to the bodies of II neurons.

II neurons- cells of the ventral and dorsal cochlear nuclei. Axons II of neurons pass to the opposite side with the formation of a trapezoid body (axons of cells of the ventral cochlear nucleus) and brain (auditory) stripes (axons of cells of the dorsal cochlear nucleus). After decussation, the axons of II neurons unite into a lateral loop, the conductors of which switch to the bodies of III neurons.

III neurons - cells of the medial geniculate body (subcortical center of hearing in the diencephalon). Their axons through the posterior pedicle of the internal capsule come to the cortex of the superior temporal gyrus (Geschl gyrus) - the cortical end of the auditory analyzer of the I signaling system (anterior gyrus) and the cortical end of the auditory analyzer of oral speech of the II signaling system (posterior gyrus).

Part of the conductors of the lateral loop (unconscious portion) pass through the medial geniculate body in transit, pass as part of the handle of the lower colliculus and switch to nuclei tecti cells (subcortical hearing centers of the midbrain) in order to close the arc of the “start reflex” (orienting reflex) in response to the auditory irritation.

5. The conductive path of the auditory analyzer (tr. n. cochlearis) (Fig. 500). The auditory analyzer performs the perception of sounds, their analysis and synthesis. The first neuron is located in the spiral node (gangl. spirale), located at the base of the hollow cochlear spindle. The dendrites of the sensitive cells of the spiral ganglion pass through the channels of the bone spiral plate to the spiral organ and terminate at the outer hair cells. The axons of the spiral node make up the auditory nerve, which enters the region of the cerebellopontine angle into the brainstem, where they end in synapses with the cells of the dorsal (nucl. dorsalis) and ventral (nucl. ventralis) nuclei.

Axons of neurons II from the cells of the dorsal nucleus form brain strips (striae medullares ventriculi quarti) located in the rhomboid fossa on the border of the bridge and the medulla oblongata. Most of the brain strip passes to the opposite side and, near the midline, is immersed in the substance of the brain, connecting to the lateral loop (lemniscus lateralis); the smaller part of the brain strip joins the lateral loop of its own side.

Axons of II neurons from the cells of the ventral nucleus are involved in the formation of the trapezoid body (corpus trapezoideum). Most of the axons pass to the opposite side, switching in the superior olive and nuclei of the trapezoid body. Another, smaller, part of the fibers ends on its own side. The axons of the nuclei of the superior olive and trapezoid body (III neuron) are involved in the formation of a lateral loop, in which there are fibers of II and III neurons. Part of the fibers of the II neuron is interrupted in the nucleus of the lateral loop (nucl. lemnisci proprius lateralis). The fibers of the II neuron of the lateral loop switch to the III neuron in the medial geniculate body (corpus geniculatum mediale). The fibers of the III neuron of the lateral loop, passing by the medial geniculate body, end in the inferior colliculus, where tr is formed. tectospinalis. Those fibers of the lateral loop that belong to the neurons of the superior olive, from the bridge penetrate into the upper legs of the cerebellum and then reach its nuclei, and the other part of the axons of the superior olive goes to the motor neurons of the spinal cord and further to the striated muscles.

Axons of neuron III, located in the medial geniculate body, passing through the posterior part of the posterior pedicle of the internal capsule, form the auditory radiance, which ends in the transverse Heschl gyrus of the temporal lobe (fields 41, 42, 20, 21, 22). Low sounds are perceived by the cells of the anterior sections of the superior temporal gyrus, and high sounds - in its posterior sections. The inferior colliculus is a reflex motor center through which tr is connected. tectospinalis. Due to this, when the auditory analyzer is stimulated, the spinal cord is reflexively connected to perform automatic movements, which is facilitated by the connection of the upper olive with the cerebellum; the medial longitudinal bundle (fasc. longitudinalis medialis) is also connected, uniting the functions of the motor nuclei of the cranial nerves.

500. Scheme of the path of the auditory analyzer (according to Sentagotai).
1 - temporal lobe; 2 - midbrain; 3 - isthmus of the rhomboid brain; 4 - medulla oblongata; 5 - snail; 6 - ventral auditory nucleus; 7 - dorsal auditory nucleus; 8 - auditory strips; 9 - olive-auditory fibers; 10 - upper olive: 11 - nuclei of the trapezoid body; 12 - trapezoid body; 13 - pyramid; 14 - lateral loop; 15 - core of the lateral loop; 16 - triangle of the lateral loop; 17 - lower colliculus; 18 - lateral geniculate body; 19 - cortical center of hearing.

hearing organ - in humans, it is paired - it allows you to perceive and analyze the whole variety of sounds of the outside world. Thanks to hearing, a person not only distinguishes sounds, recognizes their nature, location, but also masters the ability to speak.

Distinguish between the outer, middle and inner ear of a person:

outer ear - the sound-conducting part of the organ of hearing - consists of the auricle, which captures sound vibrations, and the external auditory meatus, through which sound waves are directed to the eardrum.

Auricle is a cartilaginous plate covered with perichondrium and skin; its lower part - the lobe - is devoid of cartilage and contains fatty tissue. The auricle is richly innervated: branches of the large ear, ear-temporal and vagus nerves approach it. These neural communications connect it with the deep structures of the brain that regulate the activity of internal organs. Muscles also approach the auricle: raising, moving forward, pulling back, but they are all rudimentary in nature, and a person, as a rule, cannot actively move the auricle, picking up sound vibrations, as, for example, animals do. From the auricle the sound wave hits external auditory canal 2 cm long and about 1 cm in diameter. It is covered in leather throughout. In its thickness lie the sebaceous glands, as well as sulfuric ones, which secrete earwax.

Middle ear separated from the outer tympanic membrane, formed by connective tissue. Eardrum serves as an outer wall(and there are six walls in total) narrow vertical chamber - the tympanic cavity. This cavity is the main part of the human middle ear; it contains a chain of three miniature auditory ossicles, movably connected to each other by joints. The chain is supported in a state of some tension by two very small muscles.

The first of the three bones is the malleus - fused with the tympanic membrane. Vibrations of the membrane, arising under the action of sound waves, are transmitted to the hammer, from it the second bone - the anvil, and then the third - the stirrup. The base of the stirrup is movably inserted into an oval-shaped window, "cut out" on the inner wall of the tympanic cavity. This wall(it's called a labyrinth) separates the tympanic cavity from the inner ear. In addition to the window covered by the base of the stirrup, there is another round hole in the wall - snail window closed with a thin membrane. In the thickness of the labyrinth wall passes the facial nerve.

Also applies to the middle ear. auditory or eustachian tube connecting the tympanic cavity with the nasopharynx. Through this tube 3.5 - 4.5 cm long, the air pressure in the tympanic cavity is balanced with atmospheric pressure.

inner ear as part of the organ of hearing, it is represented by the vestibule and the cochlea.

threshold - a miniature bone chamber - in front passes into the cochlea - a thin-walled bone tube twisted into a spiral. This tube makes two and a half coils around the bony axial rod, gradually tapering towards the apex. In shape, it is very reminiscent of a grape snail (hence the name).

Height from base snails to its top is 4 - 5 millimeters. The cochlear cavity is divided into three independent canals by a spiral bone protrusion and a connective tissue membrane. Upper channel that communicates with the vestibule is called the staircase of the vestibule , lower channel, or scala tympani reaches the wall of the tympanic cavity and rests directly against a round window closed by a membrane. These two canals communicate with each other through a narrow opening in the apex of the cochlea. They are filled with a specific fluid - perilymph, which vibrates under the influence of sound. First, from the shocks of the stirrup, the perilymph begins to oscillate, filling the staircase of the vestibule, and then through the hole in the region of the apex, the oscillation wave is transmitted to the perilymph of the scala tympani.

The third, membranous canal, formed by a connective tissue membrane, is, as it were, inserted into the bony labyrinth of the cochlea and repeats its shape. It is also filled with fluid - endolymph. The soft walls of the membranous canal are very sensitive to vibrations of the perilymph and transmit them to the endolymph. And already under its influence, the collagen fibers of the main membrane, protruding into the lumen of the membranous canal, begin to vibrate. On this membrane is the actual receptor apparatus of the auditory analyzer - the auditory, or Corti's organ. In the receptor hair cells of the apparatus, the physical energy of sound vibrations is converted into nerve impulses.

Sensory endings of the auditory nerve approach the hair cells, which perceive information about sound and transmit it further along the nerve fibers to the auditory centers of the brain. The higher auditory center is located in the temporal lobe of the cerebral cortex: here the analysis and synthesis of sound signals is carried out.

39. Organ of balance: the general plan of the structure. The conducting path of the vestibular analyzer.

vestibulocochlear organ in the process of evolution in animals arose as a complex organ of balance(pre-door ), which perceives the position of the body(heads) when it moves in space, and the organ of hearing. The first of them is in the form of a primitively arranged formation(static bubble) also appears in invertebrates. In fish in connection with the complication of their motor functions, first one and then the second semicircular canal is formed. In terrestrial vertebrates with their complex movements, an apparatus was formed, which in humans is represented by the vestibule and three semicircular canals located in three mutually perpendicular planes and perceiving not only the position of the body in space and its movement in a straight line, but also movements(turns of the body, head in any plane). The conductive pathway of the vestibular (statokinetic) analyzer provides conduction of nerve impulses from the hair sensory cells of the ampullar ridges(ampullae of the semicircular ducts) and spots(elliptical and spherical pouches) in the cortical centers of the cerebral hemispheres. The bodies of the first neurons statokinetic analyzer lie in the vestibular node, located at the bottom of the internal auditory canal. peripheral processes pseudounipolar cells of the vestibular node end on the hairy sensory cells of the ampullar ridges and spots. Central processes pseudounipolar cells in the form of the vestibular part of the vestibulocochlear nerve together with the cochlear part through the internal auditory opening enter the cranial cavity, and then into the brain to the vestibular nuclei lying in the vestibular field, area vesribularis rhomboid fossa. The ascending part of the fibers ends on the cells of the upper vestibular nucleus(Bekhterev). The fibers that make up the descending part end in the medial (Schwalbe), lateral (Deiters) and lower Roller) vestibular nuclei pax.

Part of axons of cells of the lateral and superior vestibular nucleus in the form of a vestibulo-spinal tract, it is directed to the spinal cord, located along the periphery at the border of the anterior and lateral cords and ends segmentally on the motor animal cells of the anterior horns, carrying out vestibular impulses to the muscles of the neck of the trunk and extremities, ensuring that the balance of the body is maintained.

Part of axons of neurons of the lateral vestibular nucleus is directed to the medial longitudinal bundle of its and the opposite side, providing a connection of the balance organ through the lateral nucleus with the nuclei of the cranial nerves (III, IV, VI nar), innervating the muscles of the eyeball, which allows you to maintain the direction of gaze, despite changes in the position of the head. Maintaining the balance of the body is largely dependent on the coordinated movements of the eyeballs and head.

Axons of cells of the vestibular nuclei form connections with the neurons of the reticular formation of the brain stem and with the nuclei of the tegmentum of the midbrain. The appearance of vegetative reactions (decreased heart rate, drop in blood pressure, nausea, vomiting, blanching of the face, increased peristalsis of the gastrointestinal tract, etc.) in response to excessive irritation of the vestibular apparatus can be explained by the presence of connections between the vestibular nuclei through the reticular formation with the nuclei of the vagus and glossopharyngeal nerves.

Conscious determination of the position of the head is achieved by the presence of connections between the vestibular nuclei and the cerebral cortex. In this case, the axons of the cells of the vestibular nuclei pass to the opposite side and are sent as part of the medial loop to the lateral nucleus of the thalamus, where they switch to III neurons.

Axons of III neurons pass through the posterior part of the posterior leg of the internal capsule and reach the cortical nucleus of the statokinetic analyzer, which is scattered in the cortex of the superior temporal and postcentral gyri, as well as in the superior parietal lobe of the cerebral hemispheres.